The Garmin Foretrex 701 is wrist or weapon mounted device is an all-in-one, state of the art ballistic calculator and a GPS/navigation unit. It contains the entire Applied Ballistics bullet and Custom Drag Model library, more than 100 slots for gun profiles, and added memory and storage to quickly calculate firing solutions in excess of 10,000 yards.
Here is an article written by Safeguard Armor about body armor for Bison Tactical. This is a great introduction for someone new looking to make a first purchase. Let us know if you need more information or just have general questions.